1. Field of Invention
This invention relates to exterior stairs, specifically terraced stairs used for landscaping customarily installed stair by stair in accordance with the topography.
2. Description of Prior Art
One of the traditional ways to make terrace stairs on sloped ground is to lay a flat piece of rock or concrete as a starter tread at the bottom of the slope where the stairs begin, and place one or more barrier bricks at far end of the treads to form a riser, The area so formed is then back filled with soil and leveled even with the top of the bricks. The first stair tread is then placed thereon, and the procedure repeated the next step and so on until the stairs reach the desired height.
The method has the advantage that it permits the installer to vary the angle of incline to accommodate the slope within the range bricks can be placed. For example, if the bricks that form the rise height are placed at farthest end of tread, the incline is the smallest, as they are placed closer to the forward the incline becomes more. Moreover, the riser bricks can be placed with yaw angle so that the stair path follows the curvature of the slope.
A paramount disadvantage of this prior art methodology is that the soil has to be compacted against the inside of the riser surface. Since the riser is not secured, it is prone to disposition. Moreover, unsecured risers may also be subsequently displaced by use, erosion and/or other forces arising from changing climatic conditions.
One possible solution is to fabricate a combined structure wherein the riser is attached permanently to the tread. While compacting of the soil is greatly facilitated, there is a loss of flexibility in that the incline becomes fixed and yaw angle is only adjustable by skewing the next tread against the installed riser, resulting in a less aesthetic frontal appearance. Other obvious solutions suggested by the problem involve adhesives such as cement to position the riser so as to bring about the desired incline and yaw angle during installation. This however, necessitates delays in that work can progress only at a rate determined by the bonding time. Moreover, this approach does not allow for correction once adhesion is complete. Another obvious alternative is to provide mechanical attachments (e.g., embedded bolts from the top of the riser adapted to fit into accordant holes in the treads). This solution too has obvious problems; the treads must have a number of threaded inserts to allow for adjustments, which are not only expensive but also unsightly.
One prior art device marketed; by American Concrete Industries Company at 1022 Minot Ave. Auburn, Me. 04210 the riser is attached to the front-bottom of tread. In this design, the incline and yaw angle are adjustable by locating the next stair in desired place. But this approach also creates another problem, namely, the soil has to be contoured to fit the next stair while the next stair is not yet in placexe2x80x94so there is an element of anticipatory fill making and compacting, which is much trial and error and labor intensive. A collateral disadvantage of this product is due to its shape and bulk. Shipment and storage require more space than separate steps and risers.
A fundamental disadvantage of all prior art structures is that they do not lend themselves to installation in open unbounded terrain. When installed in open slope without structures on both sides, rain erodes the soil adjacent to the stairs creating a ditch along both sides. This can result in unsafe conditions, which are sometimes not obvious to persons using them.
Accordingly, several objects and advantages of this invention are:
(a) to provide stairs with risers that are adjustable in location for the incline and curvature of slope;
(b) to provide stairs that have a way to secure the adjustments easily and quickly once the adjustments are made so that the soil can be easily compacted against the riser for integrity against the use and weather;
(c) to provide stairs that have a way to reverse securing if correction has to be made;
(d) to provide a structure that facilitates the fill and level of each step against an already secure and adjusted step and riser;
(e) to provide stairs that are easily stacked for shipping and storage;
(f) to provide a stair structure that reduces erosion by natural elements.
Other objects and advantages of the invention will be apparent from a consideration of the drawings and ensuing description.